Information
Definition
TN-C-S earthing is an arrangement where neutral and protective functions are combined in part of the supply and separated within the installation. It is normally assessed during product selection, circuit design, installation verification and maintenance of EV charging equipment.
Why it matters
It is closely associated with PME supplies in the UK and is central to open PEN fault considerations for EV charging. For UK users, it supports safer specification decisions and reduces the risk of misunderstanding how a charger should be protected or installed.
References
Standards and regulations
BS 7671
BS 7671 is the UK national standard for electrical installations, covering the design, erection, inspection, testing and verification of low-voltage electrical systems. Section 722 contains specific requirements for supplies to electric vehicles.
IET 01
IET 01:2024 is a non-statutory IET standard and technical specification for Open combined Protective and Neutral conductor Detection Devices used with EV charging equipment. It sets out definitions, requirements and tests for how discrete or integrated OPDD functions should respond to open PEN conductor faults.